Solid-State Image Sensor

The present disclosure relates to a solid-state image sensor, and, in particular, to a solid-state image sensor that includes a converging structure and a diverging structure that respectively correspond to different photoelectric conversion elements.

Solid-state image sensors (e.g., complementary metal-oxide semiconductor (CMOS) image sensors) have been widely used in various image-capturing apparatuses such as digital still-image cameras, digital video cameras, and the like. Signal electric charges may be generated according to the amount of light received in the light-sensing portion (e.g., photoelectric conversion element) of the solid-state image sensor. In addition, the signal electric charges generated in the light-sensing portion may be transmitted and amplified, whereby an image signal is obtained.

High dynamic range (HDR) technology realizes crisp image capture, even with extremely bright and dark areas in one scene. Moreover, the HDR function not only solves the LED flicker mitigation (LFM) issue but it can also help detect and manage complex ambient light profiles. However, in traditional solid-state image sensors, it is more difficult to achieve a high dynamic range.

According to some embodiments of the present disclosure, the solid-state image sensor includes a converging structure and a diverging structure respectively corresponding to different photoelectric conversion elements. This enhances the signal difference of the photoelectric conversion elements, thereby achieving a high dynamic range.

An embodiment of the present disclosure provides a solid-state image sensor. The solid-state image sensor includes a first photoelectric conversion element and a second photoelectric conversion element adjacent to the first photoelectric conversion element. The solid-state image sensor also includes a color filter layer disposed above the first photoelectric conversion element and the second photoelectric conversion element. The solid-state image sensor further includes a converging structure and a diverging structure disposed on the color filter layer. The converging structure corresponds to the first photoelectric conversion element. The diverging structure corresponds to the second photoelectric conversion element.

In some embodiments, the diverging structure includes pillars.

In some embodiments, the number of the pillars is four, and the four pillars are arranged symmetrically and adjacent to centers of four sides of the second photoelectric conversion element in a top view, so that diffraction occurs when light passes through the pillars.

In some embodiments, the pillars are solid transparent cubes, and each of the pillars is formed into a circle, a rectangle, or a triangle in a top view.

In some embodiments, the diverging structure includes a pillar, and an orthogonal projection of the pillar on the second photoelectric conversion element divides the second photoelectric conversion element into two regions, so that refraction occurs when light passes through the pillar.

In some embodiments, the orthogonal projection of the pillar on the second photoelectric conversion element is a hollow circular pattern or a hollow square pattern.

In some embodiments, the refractive index of the diverging structure is greater than the refractive index of air.

In some embodiments, the refractive index of the diverging structure is in a range from 1.2 to 2.5.

In some embodiments, the diverging structure includes first pillars and second pillars disposed above the first pillars.

In some embodiments, the diverging structure further includes an intermediate layer disposed between the first pillars and the second pillars and between the first pillars.

In some embodiments, each first pillar has a different diameter than each second pillar.

In some embodiments, the refractive index of the first pillars is different from the refractive index of the second pillars.

In some embodiments, there are first photoelectric conversion elements and one second photoelectric conversion element define pixels having the same size.

In some embodiments, the first photoelectric conversion elements surround the second photoelectric conversion element.

In some embodiments, eight first photoelectric conversion elements and one second photoelectric conversion element define nine pixels that form a 3×3 array, one of the pixels in the center corresponds to the second photoelectric conversion element and the diverging structure, and others of the pixel in the periphery correspond to the eight first photoelectric conversion elements and the converging structure.

In some embodiments, the first photoelectric conversion element defines a first pixel, the second photoelectric conversion element defines a second pixel, and the first pixel is larger than the second pixel.

In some embodiments, there are four first photoelectric conversion elements, and the second photoelectric conversion element is surrounded by the four first photoelectric conversion elements.

In some embodiments, the diverging structure inculudes pillars, and the pillars are diagonally arranged and correspond to two diagonal lines formed by the four first photoelectric conversion elements.

In some embodiments, the converging structure is a convex micro lens.

In some embodiments, the thickness of the diverging structure is greater than or equal to the thickness of the converging structure.

The following disclosure provides many different embodiments, or examples, for implementing different features of the subject matter provided. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, a first feature is formed on a second feature in the description that follows may include embodiments in which the first feature and second feature are formed in direct contact, and may also include embodiments in which additional features may be formed between the first feature and second feature, so that the first feature and second feature may not be in direct contact.

It should be understood that additional steps may be implemented before, during, or after the illustrated methods, and some steps might be replaced or omitted in other embodiments of the illustrated methods.

Furthermore, spatially relative terms, such as “beneath,” “below,” “lower,” “on,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to other elements or features as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

In the present disclosure, the terms “about,” “approximately” and “substantially” typically mean +/−20% of the stated value, more typically +/−10% of the stated value, more typically +/−5% of the stated value, more typically +/−3% of the stated value, more typically +/−2% of the stated value, more typically +/−1% of the stated value and even more typically +/−0.5% of the stated value. The stated value of the present disclosure is an approximate value. That is, when there is no specific description of the terms “about,” “approximately” and “substantially”, the stated value includes the meaning of “about,” “approximately” or “substantially”.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It should be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined in the embodiments of the present disclosure.

The present disclosure may repeat reference numerals and/or letters in following embodiments. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

1 FIG.A 1 FIG.B 1 FIG.A 1 FIG.B 1 FIG.A 1 FIG.B 100 100 100 100 is a partial cross-sectional view illustrating the solid-state image sensoraccording to some embodiments of the present disclosure.is a partial top view illustrating the solid-state image sensoraccording to some embodiments of the present disclosure. For example,may be the partial cross-sectional view of solid-state image sensoralong line A-A′ in, but the present disclosure is not limited thereto. It should be noted that some components of the solid-state image sensorhave been omitted inandfor the sake of brevity.

100 100 10 10 1 FIG.A 1 FIG.A Here, the solid-state image sensormay be a complementary metal-oxide semiconductor (CMOS) image sensor or a charge coupled device (CCD) image sensor, but the present disclosures is not limited thereto. As shown in, in some embodiments, the solid-state image sensora semiconductor substratewhich may be, for example, a wafer or a chip, but the present disclosure is not limited thereto. As shown in, multiple photoelectric conversion elements (e.g., photodiodes) may be formed in the semiconductor substrate.

1 FIG.A 100 11 11 11 11 11 13 13 10 Referring to, in some embodiments, the solid-state image sensorincludes a first photoelectric conversion elementL and a second photoelectric conversion elementS that is adjacent to the first photoelectric conversion elementL. Moreover, the first photoelectric conversion elementL and the second photoelectric conversion elementS may be isolated from each other by isolation structuressuch as deep trench isolation (DTI) regions or shallow trench isolation (STI) regions. The isolation structuresmay be formed in the semiconductor substrateusing etching process to form trenches and filling the trenches with an insulating or dielectric material.

1 FIG.A 100 20 10 11 11 20 20 20 2 2 5 As shown in, the solid-state image sensormay include a high dielectric-constant (high-K) filmdisposed on the semiconductor substrateand covering the first photoelectric conversion elementL and the second photoelectric conversion elementS. For example, the high-K filmmay include hafnium oxide (HfO), hafnium tantalum oxide (HfTaO), hafnium titanium oxide (HfTiO), hafnium zirconium oxide (HfZrO), tantalum pentoxide (TaO), any other suitable high-K dielectric material, or a combination thereof, but the present disclosure is not limited thereto. The high-K filmmay be formed by a deposition process. The deposition process is, for example, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), or another deposition technique. The high-K filmmay have a high-refractive index and a light-absorbing ability.

1 FIG.A 100 30 20 30 30 As shown in, the solid-state image sensormay include a buffer layerdisposed on the high-K film. For example, the buffer layermay include silicon oxides, silicon nitrides, silicon oxynitrides, any other suitable insulating material, or a combination thereof, but the present disclosure is not limited thereto. The buffer layermay be formed by a deposition process. The deposition process is, for example, spin-on coating, chemical vapor deposition, flowable chemical vapor deposition (FCVD), plasma enhanced chemical vapor deposition, physical vapor deposition (PVD), or another deposition technique.

1 FIG.A 100 32 30 13 32 32 As shown in, the solid-state image sensormay further include a metal grid structuredisposed in the buffer layerand corresponding to the isolation structures. For example, the metal grid structuremay include tungsten (W), aluminum (Al), metal nitride (e.g., titanium nitride (TiN)), any other suitable material, or a combination thereof, but the present disclosure is not limited thereto. The metal grid structuremay be formed by a deposition process and a patterning process, but the present disclosure is not limited thereto.

1 FIG.A 100 40 11 11 40 30 40 Referring to, in some embodiments, the solid-state image sensorincludes a color filter layerdisposed above the first photoelectric conversion elementL and the second photoelectric conversion elementS. In more detail, the color filter layermay be disposed on the buffer layer, but the present disclosure is not limited thereto. The color filter layermay be formed by a deposition process. Examples of the deposition process have been described above and will not be repeated here.

1 FIG.A 1 FIG.A 100 54 62 40 54 11 62 11 54 11 62 11 62 62 54 54 Referring to, in some embodiments, the solid-state image sensorincludes a converging structureand a diverging structuredisposed on the color filter layer. The converging structurecorresponds to the first photoelectric conversion elementL, and the diverging structurecorresponds to the second photoelectric conversion elementS. In other words, the converging structureis disposed above the first photoelectric conversion elementL, and the diverging structureis disposed above the second photoelectric conversion elementS. As shown in, in some embodiments, the thickness Tof the diverging structureis substantially equal to the thickness Tof the converging structure, but the present disclosure is not limited thereto.

54 54 54 In some embodiments, the converging structureis a convex micro lens. For example, the converging structuremay include a transparent material, such as glass, epoxy resin, silicone resin, polyurethane, any other applicable material, or a combination thereof, but the present disclosure is not limited thereto. The converging structuremay be formed by a photoresist reflow method, a hot embossing method, any other applicable method, or a combination thereof.

1 FIG.A 54 54 54 In the embodiment shown in, the converging structureis a semi-convex lens or a convex lens, but the present disclosure is not limited thereto. In some other embodiments, the converging structuremay be a micro-pyramid structure (e.g., circular cone, quadrangular pyramid, and so on), or a micro-trapezoidal structure (e.g., flat top cone, truncated square pyramid, and so on). Alternatively, the converging structuremay be a gradient-index structure.

1 FIG.B 1 FIG.A 1 FIG.B 11 11 54 62 62 62 62 54 62 62 62 merely shows the first photoelectric conversion elementL, the second photoelectric conversion elementS, the converging structure, and the diverging structurefor the sake of brevity. As shown inand, in some embodiments, the diverging structureincludes pillarsP. For example, the pillarsP may include materials that are the same as or similar to the converging structure, but the present disclosure is not limited thereto. In some embodiments, pillarsP are solid transparent cubes. In some embodiments, the refractive index of the diverging structureis greater than the refractive index of air. In some embodiments, the refractive index of the diverging structureis in a range from about 1.2 to about 2.5.

1 FIG.A 1 FIG.B 1 FIG.B 11 11 11 11 As shown inand, in some embodiments, multiple first photoelectric conversion elementsL and one second photoelectric conversion elementS define pixels P that have the same size. For example, the width WP of the pixel P may be about 2 μm, but the present disclosure is not limited thereto. As shown in, in some embodiments, the first photoelectric conversion elementsL surround the second photoelectric conversion elementS.

1 FIG.B 11 11 11 62 62 11 54 As shown in, in some embodiments, eight first photoelectric conversion elementsL and one second photoelectric conversion elementS define nine pixels P that form a 3×3 array. In other words, one of the pixels P in the center corresponds to the second photoelectric conversion elementS and the diverging structure(e.g., pillarsP), and others of the pixel P in the periphery correspond to the eight first photoelectric conversion elementsL and the converging structure(e.g., convex micro lens) in this embodiment.

62 62 62 62 11 11 62 62 62 1 FIG.B 1 FIG.B 1 FIG.B In some embodiments, the pillarsP are arranged symmetrically in a top view (e.g.,). In this embodiment, the number of pillarsP that correspond to one pixel P is four, but the present disclosure is not limited thereto. The number of pillarsP may be changed as needed. Moreover, in some embodiments, each pillarP is disposed adjacent to the center of each sideSS of the second photoelectric conversion elementS in a top view (e.g.,). In other words, the pillarsP may be horizontally and vertically arranged in, but the present disclosure is not limited thereto. Diffraction occurs when light passes through the diverging structuredue to the arrangement of the pillarsP, thereby changing the path of the light.

2 FIG.A 2 FIG.D 1 FIG.B 2 FIG.A 2 FIG.B 2 FIG.A 2 FIG.B 62 62 62 62 toare enlarged views of region E inaccording to some embodiments of the present disclosure. As shown in, each pillarP is formed into a circle in a top view. For example, the diameter of the circle may be greater than about 300 nm, but the present disclosure is not limited thereto. As shown in, each pillarP is formed into a rectangle in a top view. Alternatively, each pillarP is formed into a triangle in a top view. In the embodiments show inand, diffraction occurs when light passes through the pillarsP, thereby changing the path of the light.

62 62 62 62 62 62 62 62 62 62 62 In some embodiments, the degree of diffraction is affected by the thickness T, the dimension D, and refractive index of the cylinder of the diverging structure(i.e., pillarP). The refractive index of the diverging structurehas a greater impact than the dimension Dof the diverging structure, and the dimension Dof the diverging structurehas a greater impact than the thickness Tof the diverging structure.

62 62 11 11 62 11 62 11 62 11 11 62 2 FIG.C 2 FIG.D 2 FIG.C 2 FIG.D In some embodiments, the diverging structure includes one pillarP, and an orthogonal projection of the pillarP on the second photoelectric conversion elementS divides the second photoelectric conversion elementS into two regions. As shown in, the orthogonal projection of the pillarP on the second photoelectric conversion elementS is a hollow circular pattern in a top view. As shown in, the orthogonal projection of the pillarP on the second photoelectric conversion elementS is a hollow square pattern in a top view. Alternatively, the orthogonal projection of the pillarP on the second photoelectric conversion elementS may be any other pattern (e.g., a hollow triangular pattern, a hollow hexagonal pattern, or the like) that divides the second photoelectric conversion elementS into at least two regions in a top view. In the embodiments show inand, refraction occurs when light passes through the pillarP, thereby changing the path of the light.

3 FIG.A 3 FIG.E 3 FIG.A 3 FIG.E 100 100 toare partial cross-sectional views illustrating a method for forming the solid-state image sensorat various stages according to some embodiments of the present disclosure. Similarly, some components of the solid-state image sensorhave been omitted intofor the sake of brevity.

3 FIG.A 20 20 10 10 11 11 11 13 11 11 20 11 11 As shown in, a high-K filmfilmis formed on the semiconductor substrate, for example, by a deposition process. Here, the semiconductor substrateincludes a first photoelectric conversion elementL and a second photoelectric conversion elementS that is adjacent to the first photoelectric conversion elementL. Moreover, the isolation structuresare disposed between the first photoelectric conversion elementL and the second photoelectric conversion elementS, and the high-k filmcovers the first photoelectric conversion elementL and the second photoelectric conversion elementS.

3 FIG.A 30 20 32 30 13 40 30 50 40 As shown in, a buffer layeris formed on the high-K film, for example, by a deposition process. Here, a metal grid structuremay also be formed in the buffer layerand correspond to the isolation structures. Then, a color filter layeris formed on the buffer layer, for example, by a deposition process. Then, a transparent materialis formed on the color filter layer, for example, by a deposition process.

3 FIG.B 52 50 50 52 52 52 52 52 2 As shown in, a mask layeris formed on the transparent material, and then an etching process is performed to etch the transparent materialusing the mask layeras an etch mask. For example, the mask layermay include a photoresist, such as a positive photoresist or a negative photoresist. Alternately, the mask layermay be a hard mask and may include silicon oxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON), silicon carbide (SiC), silicon carbonitride (SiCN), the like, or a combination thereof. The mask layermay be a single layer or a multilayer structure any has a holeH.

52 The mask layermay be formed by a deposition process, a photolithography process, any other suitable process, or a combination thereof. For example, the deposition process includes spin-on coating, chemical vapor deposition (CVD), atomic layer deposition (ALD), the like, or a combination thereof. For example, the photolithography process may include photoresist coating (e.g., spin coating), soft baking, mask aligning, exposure, post-exposure baking (PEB), developing, rinsing, drying (e.g., hard baking), any other suitable process, or a combination thereof.

4 The etching process may include a dry etching process, a wet etching process, or a combination thereof. For example, the dry etching process may include reactive ion etch (RIE), inductively-coupled plasma (ICP) etching, neutral beam etch (NBE), electron cyclotron resonance (ERC) etching, the like, or a combination thereof. For example, the wet etching process may use, for example, hydrofluoric acid (HF), ammonium hydroxide (NHOH), or any suitable etchant.

3 FIG.C 54 11 54 As shown in, the converging structureis formed to correspond to the first photoelectric conversion elementL. For example, a reflow process may be performed to form the converging structure, but the present disclosure is not limited thereto.

3 FIG.D 56 54 56 54 As shown in, a stop layeris formed on the converging structure, so that the stop layermay cover the converging structure.

3 FIG.E 1 FIG.A 60 56 58 60 60 58 58 11 62 62 11 As shown in, another transparent materialis formed on the stop layer, for example, by a deposition process. Another mask layeris formed on transparent material, and then an etching process is performed to etch the transparent materialusing the mask layeras an etch mask. Here, the mask layercorresponds to the second photoelectric conversion elementS, so that the diverging structure(the pillarsP) as shown inis formed above the second photoelectric conversion elementS after the etching process.

4 FIG. 1 FIG.B 4 FIG. 102 102 100 102 is a partial cross-sectional view illustrating the solid-state image sensoraccording to some other embodiments of the present disclosure. The top view of the solid-state image sensormay be the same as or similar to the solid-state image sensorshown in. Similarly, some components of the solid-state image sensorhave been omitted infor the sake of brevity.

102 100 100 62 62 54 54 4 FIG. 1 FIG.A 4 FIG. The solid-state image sensorshown inhas a similar structure to the solid-state image sensorshown in. The main difference from the solid-state image sensoris that the thickness Tof the diverging structureis substantially greater than the thickness Tof the converging structurein the embodiment shown in, but the present disclosure is not limited thereto.

5 FIG. 1 FIG.B 5 FIG. 104 104 100 104 is a partial cross-sectional view illustrating the solid-state image sensoraccording to some other embodiments of the present disclosure. The top view of the solid-state image sensormay be the same as or similar to the solid-state image sensorshown in. Similarly, some components of the solid-state image sensorhave been omitted infor the sake of brevity.

104 100 100 62 104 62 1 62 2 62 1 62 62 1 62 2 62 1 62 2 62 2 62 1 5 FIG. 1 FIG.A 5 FIG. The solid-state image sensorshown inhas a similar structure to the solid-state image sensorshown in. The main difference from the solid-state image sensoris that the diverging structureof the solid-state image sensorshown inincludes first pillarsPand second pillarsPthat are disposed above the first pillarsP. That is, the diverging structuremay be a multi-layer pillar structure. In some embodiments, the refractive index of the first pillarsPis different from the refractive index of the second pillarsP. In some embodiments, each first pillarPhas a different diameter than each second pillarP, such that light may be deflected to different degrees when passing through the second pillarsPand the first pillarsP.

62 62 3 62 1 62 2 62 1 62 3 62 1 62 2 62 3 62 1 62 1 62 2 62 2 62 3 62 1 62 1 62 2 40 62 3 62 1 62 2 5 FIG. In some embodiments, the diverging structurefurther includes an intermediate layerPdisposed between the first pillarsPand the second pillarsPand between the first pillarsP. For example, the intermediate layerPmay include a different material from the first pillarsPand the second pillarsP, but the present disclosure is not limited thereto. As shown in, the intermediate layerPis disposed on top portions of the first pillarsPand connects the top portions of the first pillarsPand the bottom portions of the second pillarsPto support the second pillarsP, but the present disclosure is not limited thereto. Moreover, the intermediate layerPis disposed between the first pillarsP. Here, the first pillarsPand the second pillarsPmay be substantially perpendicular to the (top surface of) color filter layer, but the present disclosure is not limited thereto. The intermediate layerPmay be used to further separate the first pillarsPand support the second pillarsP.

6 FIG. 6 FIG. 106 106 is a partial top view illustrating the solid-state image sensoraccording to some other embodiments of the present disclosure. Similarly, some components of the solid-state image sensorhave been omitted infor the sake of brevity.

6 FIG. 11 1 11 2 1 2 1 1 2 2 As shown in, in some embodiments, the first photoelectric conversion elementL defines a first pixel P, the second photoelectric conversion elementS defines a second pixel P, and the first pixel Pis substantially larger than the second pixel P. For example, the maximum width WPof the first pixel Pis greater than the maximum width WPof the second pixel P.

6 FIG. 11 11 11 11 As shown in, in some embodiments, there are multiple first photoelectric conversion elementsL and multiple second photoelectric conversion elementsS, and each second photoelectric conversion elementS is surrounded by four first photoelectric conversion elementsL, but the present disclosure is not limited thereto.

62 11 62 6 FIG. 6 FIG. Similarly, in some embodiments, each pillarP is disposed adjacent to the center of each side of the second photoelectric conversion elementS in a top view (e.g.,). In other words, the pillarsP are diagonally arranged and correspond to two diagonal lines formed by the four first photoelectric conversion elements as shown in the embodiment of, but the present disclosure is not limited thereto.

As noted above, the solid-state image sensor according to the embodiments of the present disclosure includes a converging structure and a diverging structure respectively corresponding to different photoelectric conversion elements. This effectively enhances the signal difference of the photoelectric conversion elements (such as enhances 8.6%), thereby achieving a high dynamic range.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection should be determined through the claims. In addition, although some embodiments of the present disclosure are disclosed above, they are not intended to limit the scope of the present disclosure.

Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present disclosure should be or are in any single embodiment of the disclosure. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Thus, discussions of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same embodiment.

Furthermore, the described features, advantages, and characteristics of the disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, in light of the description herein, that the disclosure can be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the disclosure.